Field of the Invention
This invention relates to a magnification device for individuals with low vision. More particularly, the present invention relates to a handheld magnification device with a variable focus distance.
Description of the Background Art
The use of electronic magnifiers for low vision users is known in the art. These magnifiers typically include an image sensor and a lens that are configured to provide enlarged images of an associated object. One issue with magnifier cameras is depth of field. Depth of field refers to the closest and farthest distances an object can be viewed while maintaining focus. Providing a large depth of field is desirable because it allows users to view objects at various distances without having to refocus the camera. However, depth of field is often lost as the resolution of the sensor is improved. Namely, as a camera's resolution increases, the depth of field decreases. In order to compensate for the loss of depth of field, the focus must be varied. For a lens having a fixed focal length, this can be accomplished by mechanically moving the lens.
What is needed, therefore, is a high resolution magnifier camera with a means for mechanically moving the associated lens. This would permit a higher resolution sensor to be employed without diminishing the perceived depth of field when using the magnifier. The portable multi position magnifier camera of the present invention is directed at fulfilling these needs.